Discounters Aldi and Lidl reached a combined record market share in May, while Sainsbury’s clung on as the second-biggest UK grocer, according to the latest data.

The Kantar grocery market share figures for the 12 weeks to May 19, 2019 showed that Aldi and Lidl were collectively worth £344m more than in the same period in 2018 and reached a collective market share of 13.8%.

Sainsbury’s market share fell 0.5 percentage points to 15.2%, and Kantar said the grocer and its one-time prospective merger partner Asda are now “neck and neck in the number two position”. Asda also experienced a downturn in sales, falling 0.2% to 10.7%.

Aside from the discounters, the Co-op delivered the strongest bricks-and-mortar growth of all the grocers during this period, seeing sales swell 3.7%.

Consumer specialist at Kantar, Chris Hayward, said: “Shoppers are clearly enjoying their experience in-store at Co-op and have increased their number of trips by 5% in the past 12 weeks. New promotions like its frozen meal deal have also proved popular at the convenience store and sales of frozen pizza and frozen chips are up 27% and 24% respectively during the past 12 weeks.”

Tesco was the best performing of the big four grocers, recording a market share of 27.3%, with sales being predominantly driven by the performance of its own-label ranges. Morrisons remains the fourth-biggest grocer in the UK with a market share of 10.4%.

Overall the grocery market grew by 1.3% during the period, compared with a 2.7% uptick in 2018. Kantar’s Hayward said this was down to the impact of cooler weather compared to the same period in the previous year.

“This time last year we experienced the hottest May since records began and enjoyed major events like the Royal wedding and FA Cup final – so we would expect this period to be challenging for all grocers when comparing year-on-year performance.

“Sales of beer and lager, ice cream and sun care fell by 7%, 12% and 16% respectively during the past four weeks as cooler weather impacted discretionary spending.”